Abstract: Provided is a composition for forming polyurethane resin having a balance between reactivity and reducing viscosity and successfully imparting low-temperature storage stability, for use in fixing a hollow or flat sheet fiber separation membrane; and an MDI prepolymer containing a large amount of allophanate group without a metal compound and a method for producing the same while successfully controlling a reaction. Solution is provided by using a composition for forming polyurethane resin, containing a specific isocyanate group-containing compound; allophanatizing MDI with a tertiary amine catalyst without containing a metal catalyst; and reacting in the presence of at least one selected from the group consisting of a carboxylic acid amide, a sulfonic acid amide and an active methylene compound.

Abstract: Provided are a composition for forming a polyurethane resin used for a membrane sealing material, the composition having low viscosity and contributing to the formation of a membrane sealing material having reduced elution of low-molecular weight reaction products; and a membrane sealing material and a membrane module using this composition. Disclosed is a composition for forming a polyurethane resin used for a membrane sealing material, the composition including a base agent (A) and a curing agent (B), wherein the base agent (A) comprises an isocyanate group-terminated prepolymer (A1), the isocyanate group-terminated prepolymer (A1) is a reaction product between an isocyanate group-containing compound (a1) and an active hydrogen-containing compound (a2), the base agent (A) comprises diphenylmethane diisocyanate, the monomer content of the diphenylmethane diisocyanate is 35% by mass or less, and the curing agent (B) comprises a compound (b1) represented by Formula (1).

Abstract: An allophanate group-containing polyisocyanate composition that contributes to the formation of a polyurethane resin with fewer bubbles is provided. Disclosed is an allophanate group-containing polyisocyanate composition (C) including a reaction product of diphenylmethane diisocyanate (A) and a hydroxyl group-containing compound (B), wherein the hydroxyl group-containing compound (B) includes a hydroxyl group-containing polymethylsiloxane compound (B-1) in an amount of 1 ppm or more and 300 ppm or less.

Abstract: Provided are a composition for forming a polyurethane resin used for a membrane sealing material, the composition having low viscosity and contributing to the formation of a membrane sealing material having reduced elution of low-molecular weight reaction products; and a membrane sealing material and a membrane module using this composition. Disclosed is a composition for forming a polyurethane resin used for a membrane sealing material, the composition including a base agent (A) and a curing agent (B), wherein the base agent (A) comprises an isocyanate group-terminated prepolymer (A1), the isocyanate group-terminated prepolymer (A1) is a reaction product between an isocyanate group-containing compound (a1) and an active hydrogen-containing compound (a2), the base agent (A) comprises diphenylmethane diisocyanate, the monomer content of the diphenylmethane diisocyanate is 35% by mass or less, and the curing agent (B) comprises a compound (b1) represented by Formula (1).

Abstract: Provided is a composition for forming polyurethane resin having a balance between reactivity and reducing viscosity and successfully imparting low-temperature storage stability, for use in fixing a hollow or flat sheet fiber separation membrane; and an MDI prepolymer containing a large amount of allophanate group without a metal compound and a method for producing the same while successfully controlling a reaction. Solution is provided by using a composition for forming polyurethane resin, containing a specific isocyanate group-containing compound; allophanatizing MDI with a tertiary amine catalyst without containing a metal catalyst; and reacting in the presence of at least one selected from the group consisting of a carboxylic acid amide, a sulfonic acid amide and an active methylene compound.